Physicians treating the wave of patients infected with the novel coronavirus face a difficult choice.
As critically ill patients struggle to breathe, healthcare workers have deployed invasive ventilators that take on the job for them—and help protect those around them from infection. But as more information becomes available about the success of mechanical ventilation in Covid-19 patients, some doctors are questioning whether intubation is the best way to keep these patients alive.
Critically ill Covid-19 patients usually display symptoms of acute respiratory distress syndrome (ARDS)—they can’t efficiently transfer oxygen from damaged lung tissue to their blood. Typically, the first line of treatment for ARDS is a non-invasive form of assisted breathing: Doctors try to raise oxygen levels by delivering it through a nasal tube, a face mask, or helmet.
Doctors treating Covid-19 patients with ARDS at hospitals, though, may skip less invasive methods and insert a breathing tube into lungs, a process called intubation, to avoid patients’ oxygen levels from falling dangerously. Invasive ventilation is the most aggressive way to provide oxygen to patients; it literally operates their lungs for them when they cannot. But there’s another reason healthcare workers might favor ventilators over noninvasive breathing assistance: It could help prevent the spread of the disease in hospitals.
“With [Covid] patients we are really starting to bypass non-invasive ventilation, unless you have helmet masks like those Italy has been using, where the patient’s head from the shoulder up is cordoned off,” Robert Aranson, a critical care physician in Pennsylvania, told Quartz.
To be sure, intubating a patient is risky for physicians, nurses and respiratory technicians, who can be exposed to the virus during the insertion of the breathing tube. But after insertion, intubation is better at preventing the spread of coronavirus in the air than a tube or mask that doesn’t isolate the patient’s respiratory system. “We don’t want to give them high-flow oxygen because when you cough against that jet, the chances you are going to spill [the virus] further is a big problem,” says Dr. Govind Rajan, the director of clinical services in the anesthesiology department at the University of California, Irvine, Medical Center.
That problem is exacerbated by the lack of sufficient protective gear for healthcare workers and resources to separate Covid-19 patients from other sick people. In this environment, ventilators can start looking like a more attractive option. “The moment the tube goes in, the system becomes closed, the spread of the virus becomes zero,” says Rajan. To make intubation as safe as possible, hospitals are setting up special rooms for the procedure and limiting the number of healthcare workers who are present. They can also give patients paralytic drugs to stop their respiration before the procedure, rather than after.
The choice to use a ventilator is becoming more fraught as information emerges about outcomes in intubated Covid-19 patients. Critical care doctors are beginning to worry that stress caused by invasive ventilation may contribute to the grim measures of fatality among Covid-19 patients on ventilators: One recent study of 338 Covid-19 patients (pdf) in the UK who relied upon invasive ventilators to breathe found that two-thirds died. The researchers compare that to a 36% fatality rate among sufferers of viral pneumonia who relied upon invasive ventilation from 2017 to 2019.
The high rate of ventilator deaths may simply reflect the virulence of the disease, which can progress with astonishing speed, doctors say. “For Covid, by the time they come into the hospital in any kind of respiratory distress, they go downhill quickly,” Aranson says. “If patients are trending [downward] quickly, they’re going to be better off bypassing non-invasive ventilation.” In Italy, one recent study of 1,591 Covid-19 patients reported 88% received invasive ventilation.
But some clinicians believe that patients with plunging oxygen levels who would normally would be placed on a mechanical ventilator may do better receiving oxygen with less aggressive means. Measures of oxygen saturation that might suggest the need for immediate intubation may be deceiving, Dr. Martin Gillick of Harvard Medical School told STAT, because the problem is not getting oxygen into the lungs, but from the lungs into the bloodstream. In that case, using ventilators to increase the pressure of oxygen pumped into the body may do more harm than good.
Rajan echoed these concerns, saying that unlike more common causes of respiratory distress that stiffen the lungs and make ventilation a more sensible choice to get oxygen into the bloodstream, this “virus goes from the air side, hits the alveoli”—the sacs in the lungs where oxygen and carbon dioxide are exchanged—”makes them extremely inflamed and very susceptible to pressure-induced injury.”
He also worries that patients already weakened by fighting the virus and now stressed by invasive ventilation may spur an immune system overreaction known as a cytokine storm. That occurs when the immune system begins attacking the body’s own organs, and may be an explanation for the deaths of younger, otherwise healthy Covid-19 victims.
Even before Covid-19, medical researchers investigated the connection between ventilator-induced lung injuries and cytokine storms in an attempt to explain why so many sufferers of advanced respiratory distress syndrome ultimately die from multiple organ failure. But the complexity of the interaction between the lungs, the immune system, and the diseases that lead to advanced respiratory distress make it difficult to derive a clear-cut answer. Some investigators say there is no connection between ventilators and immune system overreaction.
Another worry among doctors are the new ventilators being rushed into manufacturing to make up for shortages. Typical ventilators can be carefully adjusted to change how often the patient breathes a certain volume of oxygen and at what pressure. If simpler ventilators lack the controls to configure them to a patient’s needs, they could exacerbate ventilator injuries. Nurses and respiratory technicians can take action to ensure the new ventilators are used responsibly, but they are already stretched thin by the crisis. “They are often the ones setting up the various oxygen therapies,” says Aranson. “Were it not for them, there would be no one to run these vents.”
Rajan is part of a group of doctors who have developed a design for one of those simple ventilators. The Bridge Ventilator Consortium’s goal is to make the simpler devices available for patients who need breathing assistance but have healthier lungs, in order to free up sophisticated machines for patients with damaged respiratory systems.
Now, he and his colleagues are looking at cheaper ways to build non-invasive ventilators that also prevent the spread of the virus in the air. In Italy, engineers have adapted full-face scuba masks into non-invasive ventilators.
“We do not have the technology to do non-invasive ventilation while at the same time there is no spillage happening,” Rajan says. “It’s Catch-22—if you do not intubate these patients, you risk all the healthcare providers.”